VfA delivery and implant region detection

ABSTRACT

A method includes locating the triangle of Koch region in the right atrium of a patient&#39;s heart; securing at least one electrode of an implantable lead or device to cardiac tissue from the triangle of Koch region to deliver ventricle-from-atrium (VfA) cardiac therapy; and testing the location or depth of the at least one electrode to configure VfA cardiac therapy. Locating the target implant region in the triangle of Koch region may include detecting an atrial slow pathway potential (ASP) or atrial pacing output.

The present application claims the benefit of U.S. Provisional Application No. 62/891,599, filed Aug. 26, 2019, which is incorporated herein by reference in its entirety.

The present technology is generally related to implantable medical systems, in particular, to delivering implantable medical systems.

The cardiac conduction system includes the sinus atrial (SA) node, the atrioventricular (AV) node, the bundle of His, bundle branches, and Purkinje fibers. A heartbeat is initiated in the SA node, which may be described as the natural “pacemaker” of the heart. An electrical impulse arising from the SA node causes the atrial myocardium to contract. The signal is conducted to the ventricles via the AV node which inherently delays the conduction to allow the atria to stop contracting before the ventricles begin contracting thereby providing proper AV synchrony. The electrical impulse is conducted from the AV node to the ventricular myocardium via the bundle of His, bundle branches, and Purkinje fibers.

Implantable medical devices (IMDs), such as cardiac pacemakers or implantable cardioverter defibrillators, deliver therapeutic stimulation to patients' hearts. Patients with a conduction system abnormality, such as poor AV node conduction or poor SA node function, may receive an IMD, such as a pacemaker, to restore a more normal heart rhythm and AV synchrony. Some types of IMDs, such as cardiac pacemakers, implantable cardioverter-defibrillators (ICDs), or cardiac resynchronization therapy (CRT) devices, provide therapeutic electrical stimulation to a heart of a patient via electrodes on one or more implantable endocardial, epicardial, or coronary venous leads that are positioned in or adjacent to the heart. The therapeutic electrical stimulation may be delivered to the heart in the form of pulses or shocks for pacing, cardioversion, or defibrillation. In some cases, an IMD may sense intrinsic depolarizations of the heart and control the delivery of therapeutic stimulation to the heart based on the sensing.

Delivery of therapeutic electrical stimulation to the heart can be useful in addressing cardiac conditions such as ventricular dyssynchrony that may occur in patients. Ventricular dyssynchrony may be described as a lack of synchrony or a difference in the timing of contractions in different ventricles of the heart. Significant differences in timing of contractions can reduce cardiac efficiency. CRT, delivered by an IMD to the heart, may enhance cardiac output by resynchronizing the electromechanical activity of the ventricles of the heart. CRT is sometimes referred to as “triple chamber pacing” because CRT delivers pacing to three chambers, namely, the right atrium, right ventricle, and left ventricle.

Cardiac arrhythmias may be treated by delivering electrical shock therapy for cardioverting or defibrillating the heart in addition to cardiac pacing, for example, from an ICD, which may sense a patient's heart rhythm and classify the rhythm according to an arrhythmia detection scheme in order to detect episodes of tachycardia or fibrillation. Arrhythmias detected may include ventricular tachycardia (VT), fast ventricular tachycardia (FVT), ventricular fibrillation (VF), atrial tachycardia (AT) and atrial fibrillation (AT). Anti-tachycardia pacing (ATP), a painless therapy, can be used to treat ventricular tachycardia (VT) to substantially terminate many monomorphic fast rhythms. While ATP is painless, ATP may not deliver effective therapy for all types of VTs. For example, ATP may not be as effective for polymorphic VTs, which has variable morphologies. Polymorphic VTs and ventricular fibrillation (VFs) can be more lethal and may require expeditious treatment by shock.

Dual chamber medical devices are available that include a transvenous atrial lead carrying electrodes that may be placed in the right atrium and a transvenous ventricular lead carrying electrodes that may be placed in the right ventricle via the right atrium. The dual chamber medical device itself is generally implanted in a subcutaneous pocket and the transvenous leads are tunneled to the subcutaneous pocket. A dual chamber medical device may sense atrial electrical signals and ventricular electrical signals and can provide both atrial pacing and ventricular pacing as needed to promote a normal heart rhythm and AV synchrony. Some dual chamber medical devices can treat both atrial and ventricular arrhythmias.

Intracardiac medical devices, such as a leadless pacemaker, have been introduced or proposed for implantation entirely within a patient's heart, eliminating the need for transvenous leads. A leadless pacemaker may include one or more electrodes on its outer housing to deliver therapeutic electrical signals and/or sense intrinsic depolarizations of the heart. Intracardiac medical devices may provide cardiac therapy functionality, such as sensing and pacing, within a single chamber of the patient's heart. Single chamber intracardiac devices may also treat either atrial or ventricular arrhythmias or fibrillation. Some leadless pacemakers are not intracardiac and may be positioned outside of the heart and, in some examples, may be anchored to a wall of the heart via a fixation mechanism.

SUMMARY

The techniques of this disclosure generally relate to delivering an implantable medical system for ventricle-from-atrium (VfA) cardiac therapy. These techniques may facilitate accurate delivery of an implantable medical system through the triangle of Koch region in the right atrium for pacing the left ventricle. In particular, at least one electrode of an implantable lead or device may be advanced from the triangle of Koch region through the right atrial endocardium and central fibrous body into the left ventricular myocardium of the patient's heart to deliver cardiac therapy to or sense electrical activity of the left ventricle in the basal region, septal region, or basal-septal region of the left ventricular myocardium. An atrial slow pathway potential (ASP) may be used to determine the suitability of a pacing location or depth for VfA cardiac therapy.

In one aspect, a method includes locating the triangle of Koch region in the right atrium of a patient's heart; securing at least one electrode of an implantable lead or device to cardiac tissue from the triangle of Koch region to deliver ventricle-from-atrium (VfA) cardiac therapy; and testing the location or depth of the at least one electrode to configure VfA cardiac therapy. An atrial slow pathway potential (ASP) may be used to determine the suitability of a pacing location or depth for VfA cardiac therapy. A delivery system including a mapping analyzer may be used to carry out the method.

The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram that illustrates one example of a method for delivering an implantable medical system including a lead or device for VfA cardiac therapy.

FIG. 2 is a flow diagram that illustrates one example of a method for providing an introduction pathway to the right atrium of the patient's heart that may be used with, for example, the method of FIG. 1.

FIG. 3 is a flow diagram that illustrates a first example of a method for locating the triangle of Koch region in the patient's heart that may be used with, for example, the method of FIG. 1.

FIG. 4 is a flow diagram that illustrates a second example of a method for locating the triangle of Koch region in the patient's heart that may be used with, for example, the method of FIG. 1.

FIG. 5 is a flow diagram that illustrates one example of a method for testing the location or depth of at least one electrode coupled to cardiac tissue from the triangle of Koch region that may be used with, for example, the method of FIG. 1.

FIG. 6 is a conceptual diagram that shows electrode implantation locations relative to a map of a patient's heart in a standard 17 segment view for reference during use with, for example, the methods of FIGS. 1-5.

FIG. 7 is a perspective diagram that illustrates an implantable medical system including an implantable lead and delivery sheath for use with, for example, the methods of FIGS. 1-5.

FIG. 8 is a perspective diagram that illustrates an implantable device for use with, for example, the methods of FIGS. 1-5.

FIG. 9 is a diagram of an external apparatus including electrode apparatus, display apparatus, and computing apparatus for use with, for example, the system of FIG. 7, the device of FIG. 8, and the methods of FIGS. 1-5.

FIG. 10 is a diagram that illustrates various structures of the patient's heart.

FIG. 11 is a diagram that illustrates particular electrical pathways of the patient's heart usable to detect an atrial slow pathway potential (ASP).

FIG. 12 is a conceptual diagram that illustrates a delivery assembly usable to detect the ASP for use with, for example, the methods of FIGS. 1-5, the system of FIG. 7, the device of FIG. 8, and the apparatus of FIG. 9.

FIG. 13 is a plot that illustrates an EGM signal including an ASP signature waveform usable to determine a target implant region.

FIG. 14 is a plot that illustrates ECG signals in response to high and low pacing outputs from an EGM pacing pulse usable to determine a target implant region.

DETAILED DESCRIPTION

The present disclosure provides techniques for delivering an implantable medical system for VfA cardiac therapy. These techniques may facilitate accurate delivery of an implantable medical system through the triangle of Koch region in the right atrium (RA) for pacing the left ventricle (LV). In particular, at least one electrode of an implantable lead or device may be advanced from the triangle of Koch region through the RA endocardium and central fibrous body into the LV myocardium of the patient's heart to deliver cardiac therapy to or sense electrical activity of the LV in the basal region, septal region, or basal-septal region of the LV myocardium.

As used herein, the term “or” is generally employed in its inclusive sense, for example, to mean “and/or” unless the context clearly dictates otherwise. The term “and/or” means one or all the listed elements or a combination of at least two of the listed elements.

The terms “coupled” or “connected” refer to elements being attached to each other either directly (i.e., in direct contact with each other) or indirectly (i.e., having one or more elements between and attaching the two elements). Either term may be modified by “operatively” and “operably,” which may be used interchangeably, to describe that the coupling or connection is configured to allow the components to interact to carry out functionality described in this disclosure or known to one skilled in the art having the benefit of this disclosure.

Reference will now be made to the drawings, which depict one or more aspects described in this disclosure. However, it will be understood that other aspects not depicted in the drawings fall within the scope of this disclosure. Like numbers used in the figures refer to like components, steps, and the like. However, it will be understood that the use of a reference character to refer to an element in a given figure is not intended to limit the element in another figure labeled with the same reference character. In addition, the use of different reference characters to refer to elements in different figures is not intended to indicate that the differently referenced elements cannot be the same or similar.

FIGS. 1-5 show various methods that may be used to deliver an implantable lead or device for VFA cardiac therapy. FIG. 1 shows an overall method, whereas FIGS. 2-5 show detail of some parts of the overall method. Some or all steps of these methods may be carried out by a physician, or other qualified medical professional, who may be assisted by various systems and devices described herein, for example, with respect to FIGS. 7-9. Some examples of implantation locations targeted by these various methods are shown in FIG. 6.

FIG. 1 is a flow diagram that illustrates one example of a method 100 for delivering an implantable medical system including a lead or device for VfA cardiac therapy. In general, VFA cardiac therapy may include single or multiple chamber pacing (e.g., dual or triple chamber pacing), atrioventricular (AV) synchronous pacing, asynchronous pacing, triggered pacing, cardiac resynchronization pacing, or tachycardia-related therapy. In some embodiments, VfA cardiac therapy utilizes at least one electrode coupled to the implantable lead or device implanted in the basal region, septal region, or basal-septal region (basal and septal region) of the LV myocardium of the patient's heart from the triangle of Koch region of the RA through the RA endocardium and central fibrous body. The electrode may be described as a tissue piercing electrode. The basal, septal, basal-septal regions are described in more detail with respect to FIG. 6. The triangle of Koch region is described in more detail with respect to FIGS. 7-8.

The method 100 may include providing an introduction pathway to the RA of the patient's heart 102 from outside of the patient's body to deliver at least one electrode to the RA of the patient's heart. In general, the introduction pathway to the RA includes a vein near a surface of the patient's body that leads to the RA.

The method 100 may also include locating the triangle of Koch region in the right atrium of a patient's heart 104. In some cases, the triangle of Koch region may be found in relation to particular anatomical structures, such as the tricuspid valve and the coronary sinus ostium (CSO) and the AV node, which may also be described as reference anatomical structures. In other words, the tricuspid valve or the CSO may be used as a starting point to find the triangle of Koch region.

Further, the method 100 may include securing at least one electrode of an implantable lead or device of the implantable medical system to cardiac tissue through the triangle of Koch region to deliver ventricle-from-atrium (VfA) cardiac therapy 106. Securing at least one electrode may include selecting a particular location, depth, or orientation of the implantable lead or device to properly position the at least one electrode. In general, securing at least one electrode of the implantable lead or device to cardiac tissue through the triangle of Koch region does not position the one or more electrodes into the blood volume of the LV of the patient's heart.

Also, the method 100 may include testing the location or depth of the at least one electrode to configure VfA cardiac therapy 108. If the initial location or depth of the at least one electrode is not sufficient for the desired VFA cardiac therapy, the electrode may be repositioned in terms of location or depth, for example, by adjusting the location, depth, or orientation of the implantable lead or device. Any suitable technique may be used to test the location or depth of the at least one electrode to configure VfA cardiac therapy 108, such as described with respect to FIG. 13 describing one example of identifying a location or depth for VfA cardiac therapy using an atrial slow pathway potential (ASP).

The method 100 may further include preparing a patient for VfA cardiac therapy 110. In general, any introducers or components unnecessary for delivering VfA cardiac therapy may be removed from the patient's body after the implantable medical system has been delivered. For example, a catheter may be slit, the introducer may be removed, the lead may be tied down (if there is a lead) and connected to a device (such as a pacemaker) placed in a pocket, and the pocket may be closed.

FIG. 2 is a flow diagram that illustrates one example method 102 a of providing an introduction pathway to the RA of the patient's heart 102. The method 102 may include locating a vein 120 that leads to the RA of the patient's heart. A physician may palpate the patient's body to find a vein leading to the patient's RA. In some embodiments, the subclavian vein may be used. However, any suitable vein leading to the patient's right atrium may be used. For example, the right atrium may be accessed via transvenous catheters placed through a femoral vein in the groin, as well as through superior veins such as the subclavian, brachiocephalic, or jugular veins.

The method 102 a may also include creating an entryway into the vein 122. In some embodiments, a physician may insert a needle and syringe into the vein.

The method 102 a may further include confirming that the entryway goes into the vein 124. For example, a physician may check that the needle has entered into the subclavian vein. In some embodiments, a physician may retract, or pull back on, the syringe to extract fluid from the entryway. If the color of the blood extracted into the syringe is purple, the physician may determine that the needle has entered into the subclavian vein or other suitable vein.

In addition, the method 102 a may include inserting an introducer into the vein 126 through the entryway. In general, the introducer may be used to introduce various components of an implantable medical system or delivery system through the entryway and into the RA. One example of an introducer is a sheath that may be placed in the entryway through the syringe and needle, through the subclavian vein, and into the RA. The sheath may extend from outside of the patient's body into the RA. The implantable lead or device may be advanced from outside of the patient's body, through the sheath, and into the RA.

FIG. 3 is a flow diagram that illustrates a first example method 104 a of locating the triangle of Koch region in the patient's heart 104. The method 104 a may include monitoring delivery of at least one electrode using imaging 140. For example, an imaging device or system, such as an x-ray imaging system or echocardiogram system, may be used to view one or more components being advanced into the RA. In some embodiments, a component of the delivery system or a component of the implantable lead or device may include an imaging agent, such as a radiopaque material, to provide contrast and visibility when viewed using the x-ray imaging system. In addition, other imaging agents may be used, such as a fluoroscopic contrast dye.

The method 104 a may also include advancing the implantable lead or device into the RA 142. When an introducer is used, such as a sheath, the implantable lead or device may be advanced through the introducer into the RA. The implantable lead, or delivery system for the device, may be steerable. A stylet may be coupled to the lead, or delivery system for the device, to provide a physician with control to steer the lead through the patient's body toward an implantation site.

The method 104 a may further include locating the tricuspid valve of the patient's heart using the implantable lead or device 144. In some embodiments, a physician may locate the tricuspid valve, for example, by allowing the implantable lead or device to fall into the RV or slide the device along the RA endocardium until the implantable lead or device falls into the RV to locate the tricuspid valve. A ridge of the tricuspid valve proximate to the septal wall of the right atrium above the septal leaflet of the tricuspid valve may be located. In some embodiments, a physician may locate the ridge of the tricuspid valve by moving a distal end of the implantable lead or device along the tricuspid valve until a tactile response of the ridge is detected by the physician.

In addition, the method 104 a may include moving the implantable lead or device partially toward the CSO and the AV node of the patient's heart to reach the triangle of Koch region 146, for example, after locating the tricuspid valve. In some embodiments a distal end of the implantable lead or device may be moved along the endocardium of the RA a certain distance before reaching triangle of Koch region. For example, the distal end of the implantable lead or device may be moved between 3 and 5 mm in a direction toward the CSO and the AV node. This distance is shorter than the distance required to reach either the CSO or AV node.

FIG. 4 is a flow diagram that illustrates a second example method 104 b of locating the triangle of Koch region in the patient's heart 104. The method 104 b is similar to the method 104 a and that the method 104 b may include monitoring delivery of at least one electrode using imaging 140 and advancing the implantable lead or device into the RA 142. In general, both methods 104 a, 104 b use the implantable lead or device to locate an anatomical structure that helps to locate the triangle of Koch region.

Differing from the method 104 a, the method 104 b may include locating the CSO using the implantable lead or device 148. In some embodiments, locating the CSO may include advancing the implantable lead or device into the coronary sinus (CS) of the patient's heart, which may be described as cannulating the CS. The implantable lead or device may be retracted from the CS until a distal end of the implantable lead or device reaches the CSO, just outside of the CS, based on fluoroscopy landmarks. Imaging agents may be used to highlight the CSO and the tricuspid valve.

The method 104 b may also include moving the implantable lead or device partially toward the tricuspid valve and the AV node to reach the triangle of Koch region 150. In some embodiments a distal end of the implantable lead or device may be moved along the endocardium of the RA a certain distance before reaching triangle of Koch region. For example, the distal end of the implantable lead or device may be moved between 3 and 5 mm in a direction toward the tricuspid valve and the AV node. This distance is shorter than the distance required to reach either the tricuspid valve or AV node.

FIG. 5 is a flow diagram that illustrates one example method 106 a for testing the location or depth of at least one electrode coupled to cardiac tissue from the triangle of Koch region 106. Testing the location or depth of the at least one electrode may help to ensure that the electrode will be suitable for use in delivering VfA cardiac therapy.

The method 106 a may include determining an initial implant location through the triangle of Koch region 160. For example, the initial implant location may be based on moving a distal end of the implantable lead or device a particular distance from the tricuspid valve or CSO.

The method 106 a may also include orienting the implantable lead or device at the initial implant location 162. In some embodiments, orienting the implantable lead or device may include pointing a distal end of the implantable lead or device toward the LV apex of the patient's heart. Orienting the implantable lead or device may be defined using a longitudinal axis that extends along the elongate lead or device. In some embodiments orienting the implantable lead or device may include aligning a longitudinal axis of the implantable lead or device, or a longitudinal axis of a distal end portion of the implantable lead or device, orthogonal (or perpendicular) to the surface of the triangle of Koch region at the initial implant location.

The method 106 a may also include attaching the implantable lead or device to the initial implant location 164. The implantable lead or device may be attached in any suitable manner, which may depend on the type of fixation mechanism is included. In some embodiments, the implantable lead or device includes a helical fixation assembly, which may be part of a tissue penetrating assembly including one or more electrodes. The implantable lead or device may be attached by rotating, or screwing clockwise or counterclockwise, the implantable lead or device to advance the at least one electrode into cardiac tissue forming the triangle of Koch region toward the LV. In some embodiments, the implantable lead or device includes fixation elements, which may be separate from the tissue penetrating assembly including one or more electrodes. Fixation elements may be in the form of tines that engage with cardiac tissue forming the triangle of Koch region.

The method 106 a may further include testing the initial implant location or depth 166. Any suitable testing may be performed to verify the ability of the at least one electrode to deliver VfA cardiac therapy. In some embodiments, testing may include monitoring electrical activity using one or more electrodes of the implantable lead or device. Testing may also include monitoring mechanical activity using a motion sensor of the implantable lead or device. Further, testing may include delivering test pulses using one or more electrodes of the implantable lead or device detectable by an external electrode apparatus, such as the apparatus described with respect to FIG. 9. Various pacing configurations or parameters may be tested at each location and depth.

In addition, the method 106 a may include updating the initial implant location or depth in response to the testing 168. If the testing indicates that the at least one electrode is not properly positioned to deliver VfA cardiac therapy, the initial implant location or depth may be changed. In one example, the implantable lead or device may be retracted from the cardiac tissue and reoriented at the same implant location. In another example, the implantable lead or device may be retracted from the cardiac tissue and relocated to another implantation site through the triangle of Koch region. In a further example, the implantable lead or device may be inserted further into the cardiac tissue at the same implant location. The depth may be adjusted by rotating the implantable lead or device, for example, when a helical fixation assembly is used.

Various steps of the method 106 a may be repeated until the testing indicates that the at least one electrode is properly positioned to deliver VfA cardiac therapy. Updating the initial implant location or depth 168 may only be performed, in some cases, if the at least one electrode is not properly positioned to deliver VFA cardiac therapy.

FIG. 6 is a two-dimensional (2D) ventricular map 200 of a patient's heart (e.g., a top-down view) showing the LV 202 in a standard 17 segment view and the right ventricle (RV) 204. The map 200 includes a plurality of areas 208 corresponding to different regions of a human heart. As illustrated, the areas 208 are numerically labeled 1-17 (which, e.g., correspond to a standard 17 segment model of a human heart, correspond to 17 segments of the left ventricle of a human heart, etc.). Areas 208 of the map 200 may include basal anterior area 1, basal anteroseptal area 2, basal inferoseptal area 3, basal inferior area 4, basal inferolateral area 5, basal anterolateral area 6, mid-anterior area 7, mid-anteroseptal area 8, mid-inferoseptal area 9, mid-inferior area 10, mid-inferolateral area 11, mid-anterolateral area 12, apical anterior area 13, apical septal area 14, apical inferior area 15, apical lateral area 16, and apex area 17. The inferoseptal and anteroseptal areas of the right ventricle 204 are also illustrated, as well as the right bunch branch (RBB) and left bundle branch (LBB).

In some embodiments, a tissue piercing electrode may be implanted in a target implant region in the basal region, septal region, or basal-septal region of the LV myocardium of the patient's heart, for example, through or from the triangle of Koch region of the RA through the RA endocardium and central fibrous body. With reference to map 200, the basal region includes one or more of the basal anterior area 1, basal anteroseptal area 2, basal inferoseptal area 3, basal inferior area 4, mid-anterior area 7, mid-anteroseptal area 8, mid-inferoseptal area 9, and mid-inferior area 10. With reference to map 200, the septal region includes one or more of the basal anteroseptal area 2, basal anteroseptal area 3, mid-anteroseptal area 8, mid-inferoseptal area 9, and apical septal area 14. The basal-septal region may include one or more of the basal anteroseptal area 2, basal inferoseptal area 3, mid-anteroseptal area 8, and mid-inferoseptal area 9.

In some embodiments, the target implant region may include the basal inferoseptal area 3, mid-inferoseptal area 9, at least part of basal anteroseptal area 2 near the basal inferoseptal area, and at least part of mid-anteroseptal area 8 near the mid-inferoseptal area.

In some embodiments, the tissue piercing electrode may be positioned in the high inferior/posterior basal-septal region of the LV myocardium when implanted. The high inferior/posterior basal-septal region of the LV myocardium may include a portion of at least one of the basal inferoseptal area 3 and mid-inferoseptal area 9. For example, the high inferior/posterior basal septal region may include region 206 illustrated generally as a dashed-line boundary. As shown, the dashed line boundary represents an approximation of about where the high inferior/posterior basal-septal region and may take somewhat different shape or size depending on the particular application. Without being bound by any particular theory, intraventricular synchronous pacing or activation may result from stimulating the high septal ventricular myocardium due to functional electrical coupling between the subendocardial Purkinje fibers and the ventricular myocardium.

FIG. 7 is one example of an implantable medical system, or cardiac therapy system, 300 in use with a patient 2 to deliver VfA cardiac therapy, which may be delivered using the methods of FIGS. 1-5. The system 300 may include one or more implantable medical leads or devices (which may be referred to as IMDs). In the illustrated embodiment, the system 300 includes including an implantable lead 302, which may also be described as a leaded medical device or implantable medical lead, that may be configured for single or multiple chamber therapy and implanted in a patient's heart 8. The implantable lead 302 may be advanced into the RA through an introducer 304, which may include a sheath extending through the subclavian vein into the RA.

The implantable lead 302 is shown implanted in RA of the patient's heart 8 in a target implant region 4, through which a tissue piercing electrode 306 may be advanced through the target implant region into a target implant location in the LV myocardium. In the illustration, the LV is behind the RV (see different perspective of the RV 614 and LV 618 of FIG. 10). In particular, the implantable lead 302 may include a tissue piercing electrode 306 that may be implanted in the high basal and/or septal region of the left ventricular myocardium 14 of the patient's heart from the triangle of Koch region of the right atrium through the right atrial endocardium and central fibrous body. In some embodiments, the tissue piercing electrode 306 may include or form part of a helical fixation assembly. The implantable lead 302 may be described as a ventricle-from-atrium (VfA) lead or device, which may sense or provide therapy to one or both ventricles (e.g., right ventricle, left ventricle, or both ventricles, depending on the circumstances) while being generally disposed in the RA.

The implantable lead 302 may include one or more fixation members (such as fixation members 20 in FIG. 8) that anchor a distal end of the implantable lead 302 against the atrial endocardium in a target implant region 4. The target implant region 4 may lie between the Bundle of His 5 and the coronary sinus ostium 3 and may be adjacent to a left side ridge 7 the tricuspid valve 6.

The one or more IMDs of the system 300 may include leadless or leaded IMDs. As used herein, a “leadless” device refers to a device being free of a lead extending out of the patient's heart 8. In other words, a leadless device may have a lead that does not extend from outside of the patient's heart 8 to into the inside of the patient's heart. Some leadless devices may be introduced through a vein, but once implanted, the device is free of, or may not include, any transvenous lead and may be configured to provide cardiac therapy without using any transvenous lead. In one example, a leadless device implanted in the RA, in particular, does not use a lead to operably connect to an electrode in the RA or LV when a housing of the device is positioned in the RA.

The system 300 may include one or more intracardiac IMDs, such as implantable device 400 (FIG. 8). As used herein, an “intracardiac” device refers to a device configured to be implanted entirely within the heart 8. An intracardiac IMD may include an optional leadlet, which does not extend out of the patient's heart 8.

In some embodiments, the system 300 may include multiple electrodes. A first electrode of the system 300 may be configured to sense electrical activity of the LV of the patient's heart 8 or to deliver cardiac therapy to the LV of the patient's heart. A second electrode of the system 300 may be configured to sense electrical activity of the RA of the patient's heart 8 or to deliver cardiac therapy to the RA of the patient's heart.

One or more leadless electrodes may be coupled to the housing of an IMD. An IMD having only leadless electrodes may be described as a leadless IMD. As used herein, a “leadless” electrode refers to an electrode operably coupled to a device being free of a lead, or without using a lead, extending between the electrode and the housing of the device.

A motion sensor of the system 300 may be configured to sense mechanical activity of the patient's heart 8. In some cases, the motion sensor may be configured to sense at least mechanical activity of an atrium of the patient's heart 8. The motion sensor used may be the same as or similar to the motion sensor 11 (FIG. 8). A controller of the system 300, which may include processing circuitry, may be operably coupled to one or more of the electrodes and to the motion sensor. The operable coupling may be made using a wired or wireless connection.

In the illustrated embodiment, the system 300 includes an implantable lead 302. The implantable lead 302 may be configured to sense electrical activity of the heart 8 and to deliver pacing therapy, such as CRT. The implantable lead 302 may be attached to an interior wall (such as AV septal wall 662 shown in FIG. 12) of the heart 8 via one or more fixation elements that penetrate the tissue. These fixation elements may secure the implantable lead 302 to the cardiac tissue and retain an electrode (e.g., a cathode or an anode) on the housing of the first medical device in contact with the cardiac tissue, such as the endocardium or the myocardium. In addition to delivering pacing pulses, the implantable lead 302 may be configured to sense or monitor electrical activity, in the form of one or more electrical signals, using the electrodes carried on the housing of the implantable lead 302. The electrical activity may be generated by cardiac muscle and indicative of depolarizations and repolarizations of the heart 8 at various times during the cardiac cycle.

Processing circuitry, sensing circuitry, and other circuitry configured for performing the techniques described herein with respect to the implantable lead 302 may be housed within a respective sealed housing (not shown) operably coupled to the implantable lead. The housing (or a portion thereof) may be conductive to serve as an electrode for pacing or sensing, or as an active electrode during defibrillation. As such, the housing of an IMD may be described as including a housing electrode, or housing-based electrode.

FIG. 8 shows one example of an intracardiac or leadless implantable medical device 400 and anatomical structures of the patient's heart 8 that may be used with a cardiac therapy system, which may be leadless. The device 400 may be used as an alternative to the lead 302 (FIG. 7). In other words, the device 400 and the lead 302 may be interchangeable in terms of functionality to deliver VfA cardiac therapy once implanted.

The intracardiac device 400 may include a housing 30. The housing 30 may define a hermetically-sealed internal cavity in which internal components of the device 400 reside, such as a sensing circuit, therapy delivery circuit, control circuit, memory, telemetry circuit (or communication interface), other optional sensors, and a power source. The housing 30 may be at least partially formed from electrically conductive material. Additionally, or alternatively, the housing 30 may be formed at least partially from non-conductive material.

The housing 30 may be described as extending between a distal end region 32 and a proximal end region 34 in a generally cylindrical shape to facilitate delivery. The housing 30 may include a delivery tool interface member 26, e.g., at the proximal end 34, for engaging with a delivery tool during implantation of the device 400. For example, the delivery tool interface member 26 may be used while the device 400 is advanced toward a target implant region 4 using a delivery catheter. The delivery tool or catheter may be steerable to direct the device 400 toward the target implant region 4.

All or a portion of the housing 30 may function as an electrode during cardiac therapy, for example, in sensing and/or pacing. In the example shown, the housing-based electrode 24 is shown to circumscribe a proximal portion of the housing 30. When the housing 30 includes (e.g., is formed from) an electrically conductive material, portions of the housing 30 may be electrically insulated by a non-conductive material, such as a coating, leaving one or more discrete areas of conductive material exposed to define the proximal housing-based electrode 24. When the housing 30 includes (e.g., is formed from) a non-conductive material, an electrically conductive coating or layer may be applied to one or more discrete areas of the housing 30 to form the proximal housing-based electrode 24. In other examples, the proximal housing-based electrode 24 may be a component, such as a ring electrode, that is mounted or assembled onto the housing 30. The proximal housing-based electrode 24 may be electrically coupled to internal circuitry of the device 400, e.g., via the electrically-conductive housing 30 or an electrical conductor when the housing 30 includes a non-conductive material.

In the example shown, the housing-based electrode 24 is located nearer to the housing proximal end region 34 than the housing distal end region 32 and may, therefore, be described as being a proximal housing-based electrode. In other examples, however, the housing-based electrode 24 may be located at other positions along the housing 30, for example, relatively more distally than the position shown.

At the distal end region 32, the device 400 may include a distal fixation and electrode assembly 36, which may include one or more fixation members 20, in addition to one or more dart electrodes 12 of equal or unequal length. The one or more dart electrodes 12 of the assembly 36 may be described as tissue piercing electrodes. In other embodiments (not shown), the distal fixation and electrode assembly 36 may include a helical or spiral-shaped electrode. A dart electrode or a helix electrode may also be described as a tissue piercing electrode.

The device 400 as depicted includes a single dart electrode 12 that may include a shaft 40 extending distally away from the housing distal end region 32 and may include one or more electrode elements, such as a tip electrode element 42 at or near the free, distal end region of the shaft 40. The tip electrode element 42 may have a conical or hemi-spherical distal tip with a relatively narrow tip diameter (e.g., less than about 1 millimeter (mm)) for penetrating into and through tissue layers without using a sharpened tip or needle-like tip having sharpened or beveled edges.

The shaft 40 of the dart electrode 12 may be a normally straight member and may be rigid. In other embodiments, the shaft 40 may be described as being relatively stiff but still possessing limited flexibility in lateral directions (e.g., resilient or semi-rigid). The dart electrode 12 may be configured to pierce through one or more tissue layers to position the tip electrode element 42 within a desired tissue layer, e.g., the ventricular myocardium. As such, the length or height 47 of the shaft 40 may correspond to the expected pacing site depth. If a second dart electrode 12 is employed, its length or height may be unequal to the expected pacing site depth and may be configured to act as an indifferent electrode for delivery of pacing energy to the tissue.

The one or more fixation members 20 may be described as one or more “tines” having a normally-curved position. The tines may be held in a distally extended position within a delivery tool. The distal tips of tines may penetrate the heart tissue to a limited depth before elastically curving back proximally into the normally curved position (shown) upon release from the delivery tool.

In some examples, the distal fixation and electrode assembly 36 includes a distal housing-based electrode 22. In the case of using the device 400 as a pacemaker for multiple chamber pacing (e.g., dual or triple chamber pacing) and sensing, the tip electrode element 42 may be used as a cathode electrode paired with the proximal housing-based electrode 24 serving as a return anode electrode. Alternatively, the distal housing-based electrode 22 may serve as a return anode electrode paired with tip electrode element 42 for sensing ventricular signals and delivering ventricular pacing pulses. In other examples, the distal housing-based electrode 22 may be a cathode electrode for sensing atrial signals and delivering pacing pulses to the atrial myocardium in the target implant region 4. When the distal housing-based electrode 22 serves as an atrial cathode electrode, the proximal housing-based electrode 24 may serve as the return anode paired with the tip electrode element 42 for ventricular pacing and sensing and as the return anode paired with the distal housing-based electrode 22 for atrial pacing and sensing.

As shown in this illustration, the target implant region 4 in some pacing applications is along the atrial endocardium 18, generally inferior to the AV node 15 and the His bundle 5. The dart electrode 42 may define the length or height 47 of the shaft 40 for penetrating through the atrial endocardium 18 in the target implant region 4, through the central fibrous body 16, and into the ventricular myocardium 14 without perforating through the ventricular endocardial surface 17. When the length or height 47 of the dart electrode 12 is fully advanced into the target implant region 4, the tip electrode element 42 may rest, or be positioned, within the ventricular myocardium 14, and the distal housing-based electrode 22 may be positioned in intimate contact with or close proximity to the atrial endocardium 18.

The device 400 may include a motion sensor 11, or motion detector, within the housing 30. The motion sensor 11 may be used to monitor mechanical activity, such as atrial mechanical activity (e.g., an atrial contraction) and/or ventricular mechanical activity (e.g., a ventricular contraction). In some embodiments, the motion sensor 11 may be used to detect RA mechanical activity. A non-limiting example of a motion sensor 11 includes an accelerometer. In some embodiments, the mechanical activity detected by the motion sensor 11 may be used to supplement or replace electrical activity detected by one or more of the electrodes of the device 400. For example, the motion sensor 11 may be used in addition to, or as an alternative to, the proximal housing-based electrode 24.

The mechanical activity detected by the motion sensor 11 may correspond to various heart sounds. In general, heart sounds are associated with mechanical vibrations of a patient's heart and the flow of blood through the heart valves and, thus, may be highly correlated with pressure gradients across heart valves and blood pressure. Heart sounds may be not only due to vibrations of and pressure within the heart, but may also be due to the entire cardiohemic system, e.g., blood, heart, great arteries, etc. Heart sounds may recur with each cardiac cycle and are separated and classified according to the activity associated with the vibration.

The device 400 may be implanted such that the electrode 12 is positioned to sense electrical activity or deliver pacing therapy to a specific part of the patient's LV myocardium. For example, the electrode 12 may be implanted in the basal, septal, or basal-septal region of the LV.

FIG. 9 shows one example of an external apparatus may be used to facilitate implantation or configuration of an implantable lead or device. FIG. 9 depicts one example of a system 500 of the external apparatus including electrode apparatus 510, display apparatus 530, and computing apparatus 540, in use with a patient 520.

The electrode apparatus 510 as shown includes a plurality of electrodes 512 incorporated, or included, within a band wrapped around the chest, or torso, of a patient 520. In other embodiments, the electrode apparatus 510 may include a vest upon which the plurality of electrodes 512 may be attached, or to which the electrodes 512 may be coupled. The electrode apparatus 510 is operatively coupled to the computing apparatus 540 (e.g., through one or wired electrical connections, wirelessly, etc.) to provide electrical signals from each of the electrodes to the computing apparatus 540 for analysis, evaluation, etc. Electrode apparatus may be described in U.S. Pat. No. 9,320,446 entitled “Bioelectric Sensor Device and Methods” and issued on Apr. 26, 2016, which is incorporated herein by reference in its entirety.

Although not described herein, the system 500 may further include imaging apparatus (not shown). The imaging apparatus may be any type of imaging apparatus configured to image, or provide images of, at least a portion of the patient in a noninvasive manner. For example, the imaging apparatus may not use any components or parts that may be located within the patient to provide images of the patient except noninvasive tools, such as an imaging agent. It is to be understood that the systems, methods, and interfaces described herein may further use imaging apparatus to provide noninvasive assistance to a user (e.g., a physician) to calibrate and/or deliver a cardiac pacing therapy, to locate and position a device to deliver cardiac pacing therapy, and/or to locate or select a pacing electrode or pacing vector proximate the patient's heart for cardiac pacing therapy in conjunction with the evaluation of cardiac pacing therapy.

For example, the systems, methods, and interfaces may provide image-guided navigation that may be used to navigate leads including leadless devices, electrodes, leadless electrodes, wireless electrodes, catheters, etc., within the patient's body while also providing noninvasive cardiac therapy evaluation including determining whether a paced setting is optimal or determining whether one or more selected parameters are optimal, such as selected location information (e.g., location information for the electrodes to target a particular location in the left ventricle). Systems and methods that use imaging apparatus and/or electrode apparatus may be described in U.S. Pat. No. 9,877,789 issued on Jan. 30, 2018, and entitled “Implantable Electrode Location Selection,” U.S. Pat. No. 10,251,555 issued Apr. 9, 2019, and entitled “Implantable Electrode Location Selection,” U.S. Pat. No. 9,924,884 issued on Mar. 27, 2018, and entitled “Systems, Methods, and Interfaces for Identifying Effective Electrodes,” U.S. Pat. No. 10,064,567 issued on Sep. 4, 2018, and entitled “Systems, Methods, and Interfaces for Identifying Optical-Electrical Vectors,” each of which is incorporated herein by reference in its entirety.

Imaging apparatus may be configured to capture x-ray images and/or any other alternative imaging modality. For example, the imaging apparatus may be configured to capture images, or image data, using isocentric fluoroscopy, bi-plane fluoroscopy, ultrasound, computed tomography (CT), multi-slice computed tomography (MSCT), magnetic resonance imaging (MM), high frequency ultrasound (HIFU), optical coherence tomography (OCT), intravascular ultrasound (IVUS), two-dimensional (2D) ultrasound, three dimensional (3D) ultrasound, four-dimensional (4D) ultrasound, intraoperative CT, intraoperative MM, etc. Further, it is to be understood that the imaging apparatus may be configured to capture a plurality of consecutive images (e.g., continuously) to provide video frame data. In other words, a plurality of images taken over time using the imaging apparatus may provide video frame, or motion picture, data. Additionally, the images may also be obtained and displayed in two, three, or four dimensions. In more advanced forms, four-dimensional surface rendering of the heart or other regions of the body may also be achieved by incorporating heart data or other soft tissue data from a map or from pre-operative image data captured by MRI, CT, or echocardiography modalities. Image datasets from hybrid modalities, such as positron emission tomography (PET) combined with CT, or single photon emission computer tomography (SPECT) combined with CT, could also provide functional image data superimposed onto anatomical data, e.g., to be used to navigate treatment apparatus proximate target locations (e.g., such as locations within the RA or LV) within the heart or other areas of interest.

Systems and/or imaging apparatus that may be used in conjunction with the exemplary systems and method described herein are described in U.S. Pat. App. Pub. No. 2005/0008210 to Evron et al. published on Jan. 13, 2005, U.S. Pat. App. Pub. No. 2006/0074285 to Zarkh et al. published on Apr. 6, 2006, U.S. Pat. No. 8,731,642 issued May 20, 2014, to Zarkh et al. U.S. Pat. No. 8,861,830 issued Oct. 14, 2014, to Brada et al., U.S. Pat. No. 6,980,675 to Evron et al. issued on Dec. 27, 2005, U.S. Pat. No. 7,286,866 to Okerlund et al. issued on Oct. 23, 2007, U.S. Pat. No. 7,308,297 to Reddy et al. issued on Dec. 11, 2011, U.S. Pat. No. 7,308,299 to Burrell et al. issued on Dec. 11, 2011, U.S. Pat. No. 7,321,677 to Evron et al. issued on Jan. 22, 2008, U.S. Pat. No. 7,346,381 to Okerlund et al. issued on Mar. 18, 2008, U.S. Pat. No. 7,454,248 to Burrell et al. issued on Nov. 18, 2008, U.S. Pat. No. 7,499,743 to Vass et al. issued on Mar. 3, 2009, U.S. Pat. No. 7,565,190 to Okerlund et al. issued on Jul. 21, 2009, U.S. Pat. No. 7,587,074 to Zarkh et al. issued on Sep. 8, 2009, U.S. Pat. No. 7,599,730 to Hunter et al. issued on Oct. 6, 2009, U.S. Pat. No. 7,613,500 to Vass et al. issued on Nov. 3, 2009, U.S. Pat. No. 7,742,629 to Zarkh et al. issued on Jun. 22, 2010, U.S. Pat. No. 7,747,047 to Okerlund et al. issued on Jun. 29, 2010, U.S. Pat. No. 7,778,685 to Evron et al. issued on Aug. 17, 2010, U.S. Pat. No. 7,778,686 to Vass et al. issued on Aug. 17, 2010, U.S. Pat. No. 7,813,785 to Okerlund et al. issued on Oct. 12, 2010, U.S. Pat. No. 7,996,063 to Vass et al. issued on Aug. 9, 2011, U.S. Pat. No. 8,060,185 to Hunter et al. issued on Nov. 15, 2011, and U.S. Pat. No. 8,401,616 to Verard et al. issued on Mar. 19, 2013, each of which is incorporated herein by reference in its entirety.

The display apparatus 530 and the computing apparatus 540 may be configured to display and analyze data such as, e.g., electrical signals (e.g., electrocardiogram data), cardiac information representative of one or more of mechanical cardiac functionality and electrical cardiac functionality (e.g., mechanical cardiac functionality only, electrical cardiac functionality only, or both mechanical cardiac functionality and electrical cardiac functionality), etc. Cardiac information may include, e.g., electrical heterogeneity information or electrical dyssynchrony information, surrogate electrical activation information or data, etc. that is generated using electrical signals gathered, monitored, or collected, using the electrode apparatus 510. The computing apparatus 540 may be a server, a personal computer, or a tablet computer. The computing apparatus 540 may be configured to receive input from input apparatus 542 and transmit output to the display apparatus 530. Further, the computing apparatus 540 may include data storage that may allow for access to processing programs or routines and/or one or more other types of data, e.g., for calibrating and/or delivering pacing therapy for driving a graphical user interface configured to noninvasively assist a user in targeting placement of a pacing device, and/or for evaluating pacing therapy at that location (e.g., the location of an implantable electrode used for pacing, the location of pacing therapy delivered by a particular pacing vector, etc.).

The computing apparatus 540 may be operatively coupled to the input apparatus 542 and the display apparatus 530 to, e.g., transmit data to and from each of the input apparatus 542 and the display apparatus 530. For example, the computing apparatus 540 may be electrically coupled to each of the input apparatus 542 and the display apparatus 530 using, e.g., analog electrical connections, digital electrical connections, wireless connections, bus-based connections, network-based connections, internet-based connections, etc. As described further herein, a user may provide input to the input apparatus 542 to manipulate, or modify, one or more graphical depictions displayed on the display apparatus 530 and to view and/or select one or more pieces of information related to the cardiac therapy.

Although as depicted the input apparatus 542 is a keyboard, it is to be understood that the input apparatus 542 may include any apparatus capable of providing input to the computing apparatus 540 for performing the functionality, methods, and/or logic described herein. For example, the input apparatus 542 may include a mouse, a trackball, a touchscreen (e.g., capacitive touchscreen, a resistive touchscreen, a multi-touch touchscreen, etc.), etc. Likewise, the display apparatus 530 may include any apparatus capable of displaying information to a user, such as a graphical user interface 532 including cardiac information, textual instructions, graphical depictions of electrical activation information, graphical depictions of anatomy of a human heart, images or graphical depictions of the patient's heart, graphical depictions of a leadless pacing device used to calibrate and/or deliver pacing therapy, graphical depictions of a leadless pacing device being positioned or placed to provide cardiac pacing therapy, graphical depictions of locations of one or more electrodes, graphical depictions of a human torso, images or graphical depictions of the patient's torso, graphical depictions or actual images of implanted electrodes and/or leads, etc. Further, the display apparatus 530 may include a liquid crystal display, an organic light-emitting diode screen, a touchscreen, a cathode ray tube display, etc.

The processing programs or routines stored and/or executed by the computing apparatus 540 may include programs or routines for computational mathematics, matrix mathematics, dispersion determinations (e.g., standard deviations, variances, ranges, interquartile ranges, mean absolute differences, average absolute deviations, etc.), filtering algorithms, maximum value determinations, minimum value determinations, threshold determinations, moving windowing algorithms, decomposition algorithms, compression algorithms (e.g., data compression algorithms), calibration algorithms, image construction algorithms, signal processing algorithms (e.g., various filtering algorithms, Fourier transforms, fast Fourier transforms, etc.), standardization algorithms, comparison algorithms, vector mathematics, or any other processing required to implement one or more methods and/or processes described herein. Data stored and/or used by the computing apparatus 540 may include, for example, electrical signal/waveform data from the electrode apparatus 510, dispersions signals, windowed dispersions signals, parts or portions of various signals, electrical activation times from the electrode apparatus 510, graphics (e.g., graphical elements, icons, buttons, windows, dialogs, pull-down menus, graphic areas, graphic regions, 3D graphics, etc.), graphical user interfaces, results from one or more processing programs or routines employed according to the disclosure herein (e.g., electrical signals, cardiac information, etc.), or any other data that may be necessary for carrying out the one and/or more processes or methods described herein.

Electrical activation times of the patient's heart may be useful to evaluate a patient's cardiac condition and/or to calibrate, deliver, or evaluate cardiac therapy to be or being delivered to a patient. Surrogate electrical activation information or data of one or more regions of a patient's heart may be monitored, or determined, using the electrode apparatus 510. The electrode apparatus 510 may be configured to measure body-surface potentials of a patient 520 and, more particularly, torso-surface potentials of the patient 520.

The electrodes 512 may be configured to surround the heart of the patient 520 and record, or monitor, the electrical signals associated with the depolarization and repolarization of the heart after the signals have propagated through the torso of a patient 520. Each of the electrodes 512 may be used in a unipolar configuration to sense the torso-surface potentials that reflect the cardiac signals. The interface/amplifier circuitry 516 may also be coupled to a return or indifferent electrode (not shown) that may be used in combination with each electrode 512 for unipolar sensing. In some examples, there may be about 12 to about 50 electrodes 512 spatially distributed around the torso of the patient. Other configurations may have more or fewer electrodes 512.

The computing apparatus 540 may record and analyze the electrical activity (e.g., torso-surface potential signals) sensed by electrodes 512. The computing apparatus 540 may be configured to analyze the signals from the electrodes 512 to provide as anterior and posterior electrode signals and surrogate cardiac electrical activation times, e.g., representative of actual, or local, electrical activation times of one or more regions of the patient's heart as will be further described herein. The computing apparatus 540 may be configured to analyze the signals from the electrodes 512 to provide as anterior-septal electrode signals and surrogate cardiac electrical activation times, e.g., representative of actual, or local, electrical activation times of one or more anterior-septal regions of the patient's heart, as will be further described herein, e.g., for use in calibrating, delivering, and/or evaluating pacing therapy. Further, the electrical signals measured at the left anterior surface location of a patient's torso may be representative, or surrogates, of electrical signals of the left anterior left ventricle region of the patient's heart, electrical signals measured at the left lateral surface location of a patient's torso may be representative, or surrogates, of electrical signals of the left lateral left ventricle region of the patient's heart, electrical signals measured at the left posterolateral surface location of a patient's torso may be representative, or surrogates, of electrical signals of the posterolateral left ventricle region of the patient's heart, and electrical signals measured at the posterior surface location of a patient's torso may be representative, or surrogates, of electrical signals of the posterior left ventricle region of the patient's heart. Measurement of activation times can be performed by measuring the period of time between an onset of cardiac depolarization (e.g., onset of QRS complex) and an appropriate fiducial point such as, e.g., a peak value, a minimum value, a minimum slope, a maximum slope, a zero crossing, a threshold crossing, etc.

Additionally, the computing apparatus 540 may be configured to provide graphical user interfaces depicting the surrogate electrical activation times obtained using the electrode apparatus 510. Systems, methods, and/or interfaces may noninvasively use the electrical information collected using the electrode apparatus 510 to evaluate a patient's cardiac condition and/or to calibrate, deliver, or evaluate cardiac pacing therapy to be or being delivered to the patient.

As described herein, the electrode apparatus 510 may be configured to measure electrical information (e.g., electrical signals) representing different regions of a patient's heart. For example, activation times of different regions of a patient's heart can be approximated from surface electrocardiogram (ECG) activation times measured using surface electrodes in proximity to surface areas corresponding to the different regions of the patient's heart. In at least one example, activation times of the anterior-septal region of a patient's heart can be approximated from surface ECG activation times measured using surface electrodes in proximity to surface areas corresponding to the anterior-septal region of the patient's heart. That is, a portion of the set of electrodes 512, and not the entire set, can be used to generate activation times corresponding to a particular location of the patient's heart that the portion of the set of electrodes corresponds to.

The systems, methods, and interfaces may be used to provide noninvasive assistance to a user in the evaluation of a patient's cardiac health or status, and/or the evaluation of cardiac therapy such as CRT by use of the electrode apparatus 510 (e.g., cardiac therapy being presently-delivered to a patient during implantation or after implantation). Further, the systems, methods, and interfaces may be used to assist a user in the configuration, or calibration, of the cardiac therapy, such as CRT, to be or being delivered to a patient.

Electrical activity may be monitored using a plurality of external electrodes, such as electrodes 512. The electrical activity can be monitored by a plurality of electrodes during pacing therapy or in the absence of pacing therapy. The monitored electrical activity can be used to evaluate pacing therapy to a patient. The electrical activity monitored using the ECG belt described can be used to evaluate at least one paced setting of the pacing therapy on the heart. As an example, a paced setting can be any one parameter or a combination of parameters including, but not limited to, electrode position, pacing polarity, pacing output, pacing pulse width, timing at which ventricular pacing is delivered relative to atrial timing, pacing rate, etc. Further, as an example, the location of the leadless device or a pacing lead can include a location in the right ventricle, left ventricle, or right atrium.

Further, body-surface isochronal maps of ventricular activation can be constructed using the monitored electrical activity during pacing therapy or in the absence of pacing therapy. The monitored electrical activity and/or the map of ventricular activation can be used to generate electrical heterogeneity information (EHI). The electrical heterogeneity information can include determining metrics of electrical heterogeneity. The metrics of electrical heterogeneity can include a metric of standard deviation of activation times (SDAT) of electrodes on a left side of a torso of the patient and/or a metric of mean left ventricular activation time (LVAT) of electrodes on the left side of the torso of the patient. A metric of LVAT may be determined from electrodes on both the anterior and posterior surfaces, which are more proximal to the left ventricle. The metrics of electrical heterogeneity information can include a metric of mean right ventricular activation time (RVAT) of electrodes on the right side of the torso of the patient. A metric of RVAT may be determined from electrodes on both the anterior and posterior surfaces which are more proximal to the right ventricle. The metrics of electrical heterogeneity can include a metric of mean total activation time (mTAT) taken from a plurality of electrode signals from both sides of the torso of the patient, or it may include other metrics (e.g., standard deviation, interquartile deviations, a difference between a latest activation time and earliest activation time) reflecting a range or dispersion of activation times on a plurality of electrodes located on the right side of the patient torso or left side of the patient torso, or combining both right and left sides of the patient torso. The metrics of electrical heterogeneity information can include a metric of anterior-septal activation times (ASAT) of electrodes on the torso in close proximity to the anterior-septal portion of the heart.

Electrical heterogeneity information (EHI) may be generated during delivery of pacing therapy at one or more paced settings. The electrical heterogeneity information can be generated using metrics of electrical heterogeneity. As an example, the metrics of electrical heterogeneity can include one or more of an SDAT, an LVAT, an RVAT, an mTAT, and an ASAT. In another example, only ASAT may be determined and further used, and/or ASAT may be more heavily weighted than other values.

One or more paced settings associated with the pacing therapy may be evaluated. A paced setting can include a plurality of pacing parameters. The plurality of pacing parameters can be optimal if the patient's cardiac condition improves, if the pacing therapy is effectively capturing a desired portion of the RA, RV, or LV, and/or if a metric of electrical heterogeneity improves by a certain threshold compared to a baseline rhythm or therapy. The determination of whether the paced setting is optimal can be based on at least one metric of electrical heterogeneity generated from electrical activity during pacing (and also, in some cases, during native conduction, or in the absence of pacing). The at least one metric can include one or more of an SDAT, an LVAT, an RVAT, an mTAT, and an ASAT.

Further, the plurality of pacing parameters can be optimal if a metric of electrical heterogeneity is greater than or less than a particular threshold, and/or if the location of the pacing therapy to excite the left ventricle causes a particular pattern of excitation of the muscle fibers in the heart. In addition, the plurality of pacing parameters can be optimal if a metric of electrical heterogeneity indicates a correction of a left bundle branch block (LBBB), and/or if a metric of electrical heterogeneity indicates a complete engagement of a Purkinje system, etc. As an example, a metric of electrical heterogeneity of an ASAT less than or equal to a threshold (e.g., a threshold of 30 ms) and an LVAT less than or equal to a threshold (e.g., a threshold of 30 ms) can indicate a correction of an LBBB, and thus, the paced setting is optimal. As an example, a metric of electrical heterogeneity of an RVAT less than or equal to a threshold (e.g., a threshold of 30 ms), an ASAT less than or equal to a threshold (e.g., a threshold of 30 ms), and an LVAT less than or equal to a threshold (e.g., a threshold of 30 ms) can indicate a complete engagement of the Purkinje system, and thus the paced setting is may be optimal.

The paced setting can be determined to be optimal in response to the pacing therapy using the paced setting being acceptable, being beneficial, being indicative of complete engagement of patient's native cardiac conduction system, being indicative of correction of a ventricular conduction disorder (e.g., left bundle branch block), etc. A paced setting can include one or more of a pacing electrode position (including one or more of a depth, an angle, an amount of turn for a screw-based fixation mechanism, etc.), a voltage, a pulse width, an intensity, a pacing polarity, a pacing vector, a pacing waveform, a timing of the pacing delivered relative to an intrinsic or paced atrial event or relative to the intrinsic His bundle potential, and/or a pacing location, etc. A pacing vector can include any two or more pacing electrodes such as, e.g., a tip electrode to a can electrode, a tip electrode to a ring electrode etc., that are used to deliver the pacing therapy, etc. The pacing location can refer to the location of any of the one or more pacing electrodes that are positioned using a lead, a leadless device, and/or any device or apparatus configured to deliver pacing therapy.

A paced setting for therapy may be adjusted. The paced setting can be adjusted in response to the paced setting being not optimal. The paced setting can be adjusted in response to the paced setting being within an optimal range but in order to determine whether the paced setting can be at a position within the optimal range that is more beneficial, more useful, more functional, etc., for the pacing therapy. The paced setting could be adjusted to find the most optimal metric of electrical heterogeneity.

A determination of whether the paced setting is optimal can be based on a particular metric of electrical heterogeneity using an ECG belt. In at least one example, the paced setting can be adjusted at intervals that correlate with a change in the metric of electrical heterogeneity until the metric of electrical heterogeneity is at or proximate a particular metric value. For instance, the adjusting of the paced setting can cause the metric of electrical heterogeneity to approach a particular threshold metric of electrical heterogeneity and, as the metric approaches the particular threshold, the rate at which the paced setting is adjusted can be slowed down. Put another way, as the metric of electrical heterogeneity is further from the particular threshold metric, the paced setting can be adjusted more quickly and as the metric of electrical heterogeneity gets closer to the particular threshold metric, the paced setting can be adjusted more slowly until the metric of electrical heterogeneity is at the particular threshold metric.

During implantation, various techniques may be used to determine whether the correct target implant region 4 has been reached in the triangle of Koch region before attempting to implant the IMD. In some embodiments, the target implant region 4 may be identified using a slow pathway signal measured using a tip of a mapping electrode of a delivery assembly or delivery catheter. In some embodiments, the target implant region 4 may be identified by testing pacing output with a tip of a mapping electrode of a delivery assembly or delivery catheter and stepping down the pacing output until a virtual ventricular to atrial pacing transit ECG pattern is detected. Using such techniques to appropriately identify the target implant region 4 before introducing the IMD may facilitate the overall implantation process.

With reference to FIG. 10, pacing techniques generally involve pacing one or more of the four chambers of patient's heart 8, including the right atrium (RA) 612, right ventricle (RV) 614, left ventricle (LV) 616, and left atrium (LA) 618 all of which are shown in the anterior view of a frontal section of patient's heart 8. Some therapeutic pacing techniques involve the cardiac conduction system. The cardiac conduction system, like a “superhighway,” may be described as quickly conducting electrical pulses whereas pacing cardiac muscle tissue may slowly conduct electrical pulses, like “traveling on a dirt road.” The cardiac conduction system includes SA node 620, atrial internodal tracts 622, 623, 624 (i.e., anterior internodal 622, middle internodal 623, and posterior internodal 624), AV node 15, His bundle 5 (also known as the atrioventricular bundle or bundle of His), and bundle branches including the left bundle branch (LBB) 630 and the right bundle branch (RBB) 632. FIG. 10 also shows the arch of aorta 634 and Bachman's bundle 636.

The SA node 15, located at the junction of the superior vena cava (SVC) 638 and RA 612, is considered to be the natural pacemaker of the heart since it continuously and repeatedly emits electrical impulses. The electrical impulse spreads through the muscles of RA 612 to LA 618 to cause synchronous contraction of the atria. Electrical impulses are also carried through atrial internodal tracts to AV node 15—the sole connection between the atria and the ventricles.

Conduction through the tissue of the AV node 15 takes longer than through the atrial tissue, resulting in a delay between atrial contraction and the start of ventricular contraction. The AV delay, which is the delay between atrial contraction and ventricular contractor, allows the atria to empty blood into the ventricles. Then, the valves between the atria and ventricles close before causing ventricular contraction via branches of the His bundle 5.

His bundle 5 is located in the membranous atrioventricular septum near the annulus of the tricuspid valve. The tricuspid valve 6 is between the RA 612 and the RV 614. His bundle 5 splits into the LBB 630 and RBB 632 and are formed of specialized fibers called “Purkinje fibers” 640. Purkinje fibers 640 may be described as rapidly conducting an action potential down the ventricular septum, spreading the depolarization wavefront quickly through the remaining ventricular myocardium, and producing a coordinated contraction of the ventricular muscle mass.

FIG. 11 is a diagram that illustrates particular electrical pathways of the patient's heart 8 and one example of a target implant region 4 suitable for VfA cardiac therapy. In the illustrated embodiment, the patient's heart 8 defines a fast pathway 650 from the AV node 15 to the target implant region 4, which may be described as part of the conduction system of the heart 8. The patient's heart 8 also defines a slow pathway 652 from the target implant region 4 to the AV node 15, which may also be described as part of the cardiac tissue. The target implant region 4 may also be described as the slow path area. The target implant region 4 may be determined to be suitable based upon electrical signals indicating the ASP is detected. Detection of the ASP may indicate that the target implant region 4 within the triangle of Koch region 654 has been reached using an electrode.

FIG. 12 is a conceptual diagram that illustrates one example of a delivery assembly 660 fixed to the AV septal wall 662 of the patient's heart 8, which may be used to implant a leaded or leadless IMD. The delivery assembly 660 may be described as a delivery catheter. The delivery assembly 660 may include a mapping electrode 664, which may be inserted into the AV septal wall 662 through the target implant region 4 in the triangle of Koch region 106. The mapping electrode 664 may be used to test potential implantation site locations and different depths within the AV septal wall 662, for example, until an ASP is detected.

In some embodiments, the mapping electrode 664 is disposed on a guide wire 666. The guide wire 666 may be described as a mapping guide wire. Additionally, or alternatively, the delivery assembly 660 may include an electrically conductive fixation element on a sheath may be used to provide a mapping electrode 668.

The mapping electrode 664 and the mapping electrode 668 may each be electrically coupled to an individual conductor extending between a distal portion and a proximal portion of the delivery assembly 660. The conductor may be coupled to a proximal contact, such as a proximal end ring, which may be connected to an analyzer 670 to facilitate mapping. In particular, the analyzer 670 may be any suitable electrophysiological (EP) analyzer configured to analyze electrogram (EGM) signals and/or ECG signals for mapping selected by one skilled in the art having the benefit of this disclosure. The analyzer may include a controller having processing circuitry and memory.

In general, any suitable delivery assembly may be used to deliver a leaded or leadless 1 MB. Examples of delivery assemblies that may be used include those described in U.S. Provisional Application No. 62/914,937 (Hine et al.), filed Oct. 14, 2019, and U.S. Provisional Application No. 62/948,366 (Hine et al.), filed Dec. 16, 2019, which are incorporated herein by reference.

FIG. 13 is a plot 680 that illustrates one example of an electrophysiology (EP) mapping signal, or EGM signal 682, which may be measured using an EP analyzer. In particular, a mapping electrode implanted in a target implant region may measure the EGM signal 682. As can be seen, particularly in exploded view of region 684, an ASP signature waveform 686 is detected in the EGM signal 682 may indicate that the mapping electrode is appropriately implanted in a suitable target implant region within the triangle of Koch region.

In some embodiments, the ASP signature waveform 686 may be identified as having multiple deflections. As illustrated, the ASP signature waveform 686 may include four “peaks” (local maxima) and three “valleys” (local minima). Collectively, the local maxima and minima may be described as deflection points. As shown, the ASP signature waveform 686 includes seven deflection points. In general, the ASP waveform 686 may include more local maxima and minima than other waveforms that may be detected in the EGM signal 682.

Other ECG and EGM signals are shown for reference. In the illustrated embodiment, various ECG signals 688 are shown (V1, I, and II) and other EGM signals, such as a His bundle electrode signal 690 and a proximal coronary sinus electrode signal 692. The EGM signal 682 may also be described as an RA electrode signal.

FIG. 14 is a plot 700 that illustrates one example of a mapping signal, or EGM signal 702, which includes delivery of test pacing, and various ECG signals 708, which may be used to measure the response to the pacing signal using an EP analyzer. In some embodiments, test pacing pulses may be provided to a potential implant region starting at a higher pacing output, such as 10 volts (V) for 1 ms, and reducing the pacing output to a lower pacing output, such as 0.5 V for 1 ms. The potential implant region may be identified as a suitable target implant region in response to a virtual ventricular to atrial pacing transit ECG pattern is detected in the ECG signals 708.

In the plot 700, test pacing with high pacing outputs around time windows 704 are shown with respect to the EGM signal 702 and corresponding ECG signals 708 measured, which indicate pacing of the ventricle. Test pacing with lower pacing outputs around time windows 706 are shown with respect to the EGM signal 702 and corresponding ECG signals 708 measured, which indicate a virtual ventricular to atrial pacing transit ECG pattern. In general, higher pacing outputs may pace both the ventricle and the atrium, whereas lower pacing outputs capable of pacing only the atrium may be suitable as target implant regions.

Illustrative Embodiments

While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the specific illustrative embodiments provided below. Various modifications of the illustrative embodiments, as well as additional embodiments of the disclosure, will become apparent herein.

In embodiment A1, a method comprises locating the triangle of Koch region in the right atrium of a patient's heart; securing at least one electrode of an implantable lead or device to cardiac tissue from the triangle of Koch region to deliver ventricle-from-atrium (VfA) cardiac therapy; and testing the location or depth of the at least one electrode to configure VfA cardiac therapy.

In embodiment A2, a method comprises the method according to embodiment A1, further comprising providing an introduction pathway to deliver at least one electrode to the right atrium of the patient's heart.

In embodiment A3, a method comprises the method according to embodiment A2, wherein providing the introduction pathway to the right atrium comprises one or more of:

-   -   locating a vein that leads to the right atrium of the patient's         heart;     -   creating an entryway into the vein;     -   confirming that the entryway goes into the vein; and     -   inserting an introducer into the vein through the entryway.

In embodiment A4, a method comprises the method according to any A embodiment, wherein locating the triangle of Koch region comprises one or more of:

-   -   monitoring delivery of the at least one electrode using imaging;     -   advancing the implantable lead or device into the right atrium;     -   locating the tricuspid valve of the patient's heart using the         implantable lead or device; and     -   moving the implantable lead or device partially toward the         coronary sinus ostium and the atrioventricular node of the         patient's heart to reach the triangle of Koch region.

In embodiment A5, a method comprises the method according to embodiment A4, wherein locating the tricuspid valve comprises locating a ridge of the tricuspid valve proximate to the septal wall of the right atrium above the septal leaflet of the tricuspid valve.

In embodiment A6, a method comprises the method according to any embodiment A1-A3, wherein locating the triangle of Koch region comprises one or more of:

-   -   monitoring delivery of the at least one electrode using imaging;     -   advancing the implantable lead or device into the right atrium;     -   locating the coronary sinus ostium using the implantable lead or         device; and     -   moving the implantable lead or device partially toward the         tricuspid valve and the atrioventricular node to reach the         triangle of Koch region.

In embodiment A7, a method comprises the method according to embodiment A6, wherein locating the coronary sinus ostium comprises:

-   -   advancing the implantable medical lead or device into the         coronary sinus of the patient's heart; and     -   retracting the implantable medical lead or device until a distal         end of the implantable medical lead or device reaches the         coronary sinus ostium.

In embodiment A8, a method comprises the method according to any A embodiment, wherein securing at least one electrode of the implantable lead or device to cardiac tissue from the triangle of Koch region to deliver VfA cardiac therapy comprises one or more of:

-   -   determining an initial implant location through the triangle of         Koch region;     -   orienting the implantable lead or device at the initial implant         location;     -   attaching the implantable lead or device to the initial implant         location;     -   testing the initial implant location and depth; and     -   updating the initial implant location or depth in response to         the testing.

In embodiment A9, a method comprises the method according to embodiment A8, wherein orienting the implantable lead or device comprises pointing a distal end of the implantable lead or device toward the left ventricular apex of the patient's heart.

In embodiment A10, a method comprises the method according to embodiment A8 or A9, wherein testing the initial implant location comprises one or more of:

-   -   monitoring electrical activity using one or more electrodes of         the implantable lead or device;     -   monitoring mechanical activity using a motion sensor of the         implantable lead or device; and     -   delivering test pulses using one or more electrodes of the         implantable lead or device detectable by an external electrode         apparatus.

In embodiment A11, a method comprises the method according to any A embodiment, further comprising preparing a patient for VfA cardiac therapy.

In embodiment A12, a method comprises the method according to any A embodiment, wherein securing the at least one electrode of the implantable lead or device to cardiac tissue through the triangle of Koch region does not position the one or more electrodes into the blood volume of the left ventricle of the patient's heart.

In embodiment A13, a method comprises the method according to any A embodiment, wherein securing the at least one electrode of an implantable lead or device to cardiac tissue through the triangle of Koch region comprises advancing the at least one electrode from the triangle of Koch region through the right atrial endocardium and central fibrous body into the left ventricular myocardium of the patient's heart to deliver cardiac therapy to or sense electrical activity of the left ventricle in the basal region, septal region, or basal-septal region of the left ventricular myocardium.

In embodiment A14, a method comprises the method according to any A embodiment, wherein locating the triangle of Koch region in the right atrium of a patient's heart comprises testing whether an atrial slow pathway potential (ASP) is detected at a potential target implant region using at least one electrode of a delivery assembly.

In embodiment A15, a method comprises the method according to embodiment A14, wherein testing whether an ASP is detected comprises determining whether electrical activity detected by the at least one electrode comprises a deflection pattern indicative of ASP.

In embodiment A16, a method comprises the method according to any A embodiment, wherein locating the triangle of Koch region in the right atrium of a patient's heart comprises testing whether a pacing output at a potential target implant region paces the atrium without pacing the ventricle of the patient's heart using at least one electrode of a delivery assembly.

In embodiment A17, a method comprises the method according to embodiment A16, wherein testing whether a pacing output at a potential target implant region comprises:

-   -   delivering a pacing output to capture ventricular pacing; and     -   reducing the pacing output until atrial pacing is captured and         ventricular pacing is not captured.

In embodiment B1, a delivery assembly comprises:

-   -   a mapping electrode configured to be advanced into a potential         target implant region in the triangle of Koch region; and     -   a mapping analyzer operably coupled to the mapping electrode         configured to determine whether an atrial slow pathway potential         (ASP) is detected at the potential target implant region using         the mapping electrode.

In embodiment C1, a delivery assembly comprises:

-   -   a mapping electrode configured to be advanced into a potential         target implant region in the triangle of Koch region; and     -   a mapping analyzer operably coupled to the mapping electrode         configured to determine whether a pacing output at a potential         target implant region paces the atrium without pacing the         ventricle of the patient's heart using at least one electrode of         a delivery assembly.

The embodiment of B1 or C1, wherein the mapping analyzer is configured to carry out the method according to any one of embodiments A14 to A17.

Thus, various techniques related to VfA delivery are disclosed. It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

All references and publications cited herein are expressly incorporated herein by reference in their entirety for all purposes, except to the extent any aspect directly contradicts this disclosure.

All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.

Terms related to orientation, such as “proximal,” “distal,” “top,” “bottom,” “side,” and “end,” are used to describe relative positions of components and are not meant to limit the absolute orientation of the embodiments contemplated.

As used herein, the term “configured to” may be used interchangeably with the terms “adapted to” or “structured to” unless the content of this disclosure clearly dictates otherwise.

The singular forms “a,” “an,” and “the” encompass embodiments having plural referents unless its context clearly dictates otherwise.

The phrases “at least one of,” “comprises at least one of,” and “one or more of” followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

As used herein, “have,” “having,” “include,” “including,” “comprise,” “comprising” or the like are used in their open-ended sense, and generally mean “including, but not limited to.” It will be understood that “consisting essentially of” “consisting of,” and the like are subsumed in “comprising,” and the like.

Reference to “one embodiment,” “an embodiment,” “certain embodiments,” or “some embodiments,” etc., means that a particular feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of such phrases in various places throughout are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments. 

What is claimed is:
 1. A method comprising: locating the triangle of Koch region in the right atrium of a patient's heart; securing at least one electrode of an implantable lead or device to cardiac tissue from the triangle of Koch region to deliver ventricle-from-atrium (VfA) cardiac therapy; and testing the location or depth of the at least one electrode to configure VfA cardiac therapy.
 2. The method according to claim 1, further comprising providing an introduction pathway to deliver at least one electrode to the right atrium of the patient's heart.
 3. The method according to claim 2, wherein providing the introduction pathway to the right atrium comprises one or more of: locating a vein that leads to the right atrium of the patient's heart; creating an entryway into the vein; confirming that the entryway goes into the vein; and inserting an introducer into the vein through the entryway.
 4. The method according to claim 1, wherein locating the triangle of Koch region comprises one or more of: monitoring delivery of the at least one electrode using imaging; advancing the implantable lead or device into the right atrium; locating the tricuspid valve of the patient's heart using the implantable lead or device; and moving the implantable lead or device partially toward the coronary sinus ostium and the atrioventricular node of the patient's heart to reach the triangle of Koch region.
 5. The method according to claim 4, wherein locating the tricuspid valve comprises locating a ridge of the tricuspid valve proximate to the septal wall of the right atrium above the septal leaflet of the tricuspid valve.
 6. The method according to claim 1, wherein locating the triangle of Koch region comprises one or more of: monitoring delivery of the at least one electrode using imaging; advancing the implantable lead or device into the right atrium; locating the coronary sinus ostium using the implantable lead or device; and moving the implantable lead or device partially toward the tricuspid valve and the atrioventricular node to reach the triangle of Koch region.
 7. The method according to claim 6, wherein locating the coronary sinus ostium comprises: advancing the implantable medical lead or device into the coronary sinus of the patient's heart; and retracting the implantable medical lead or device until a distal end of the implantable medical lead or device reaches the coronary sinus ostium.
 8. The method according to claim 1, wherein securing at least one electrode of the implantable lead or device to cardiac tissue from the triangle of Koch region to deliver VfA cardiac therapy comprises one or more of: determining an initial implant location through the triangle of Koch region; orienting the implantable lead or device at the initial implant location; attaching the implantable lead or device to the initial implant location; testing the initial implant location and depth; and updating the initial implant location or depth in response to the testing.
 9. The method according to claim 8, wherein orienting the implantable lead or device comprises pointing a distal end of the implantable lead or device toward the left ventricular apex of the patient's heart.
 10. The method according to claim 8, wherein testing the initial implant location comprises one or more of: monitoring electrical activity using one or more electrodes of the implantable lead or device; monitoring mechanical activity using a motion sensor of the implantable lead or device; and delivering test pulses using one or more electrodes of the implantable lead or device detectable by an external electrode apparatus.
 11. The method according to claim 1, further comprising preparing a patient for VfA cardiac therapy.
 12. The method according to claim 1, wherein securing the at least one electrode of the implantable lead or device to cardiac tissue through the triangle of Koch region does not position the one or more electrodes into the blood volume of the left ventricle of the patient's heart.
 13. The method according to claim 1, wherein securing the at least one electrode of an implantable lead or device to cardiac tissue through the triangle of Koch region comprises advancing the at least one electrode from the triangle of Koch region through the right atrial endocardium and central fibrous body into the left ventricular myocardium of the patient's heart to deliver cardiac therapy to or sense electrical activity of the left ventricle in the basal region, septal region, or basal-septal region of the left ventricular myocardium.
 14. The method according to claim 1, wherein locating the triangle of Koch region in the right atrium of a patient's heart comprises testing whether an atrial slow pathway potential (ASP) is detected at a potential target implant region using at least one electrode of a delivery assembly.
 15. The method of claim 14, wherein testing whether an ASP is detected comprises determining whether electrical activity detected by the at least one electrode comprises a deflection pattern indicative of ASP.
 16. The method according to claim 1, wherein locating the triangle of Koch region in the right atrium of a patient's heart comprises testing whether a pacing output at a potential target implant region paces the atrium without pacing the ventricle of the patient's heart using at least one electrode of a delivery assembly.
 17. The method according to claim 16, wherein testing whether a pacing output at a potential target implant region comprises: delivering a pacing output to capture ventricular pacing; and reducing the pacing output until atrial pacing is captured and ventricular pacing is not captured.
 18. A delivery assembly comprising: a mapping electrode configured to be advanced into a potential atrial pacing target implant region in the triangle of Koch region, the potential atrial pacing target implant region being a location to pace the right atrium; and a mapping analyzer operably coupled to the mapping electrode configured to determine whether an atrial slow pathway potential (ASP) is detected at the potential atrial pacing target implant region using the mapping electrode.
 19. A delivery assembly comprising: a mapping electrode configured to be advanced into a potential target implant region in the triangle of Koch region; and a mapping analyzer operably coupled to the mapping electrode configured to determine whether a pacing output at a potential target implant region paces the atrium without pacing the ventricle of the patient's heart using at least one electrode of a delivery assembly.
 20. The delivery assembly of claim 19, wherein to determine whether a pacing output at a potential target implant region paces the atrium without pacing the ventricle, the mapping analyzer is further configured to: deliver a pacing output to capture ventricular pacing; and reduce the pacing output until atrial pacing is captured and ventricular pacing is not captured. 